1. It's been a long time./It's been forever./ It's been ages.
2. Long time no see./ Long time no talk.
3. You haven't changed a bit.
4. Look who's here.
5. Look what the cat dragged in (or coughed up).
6. What are you up to these days?
7. How come you never call me?
8. Did you get your hair done?
9. Tell your sister I said hi.